Marcel Déat (March 7, 1894-January 5, 1955) was a French Fascist and politician prior to and during World War II.

Born in Guerigny , Déat became a member of the French Socialist Party in 1914. While Déat attended the École Normale Supérieure (entered in 1914) and worked to get a philosophy degree, World War I broke out. Déat entered the French Army as a private and saw active duty, winning the Legion d'Honneur and five bravery citations. By the war’s end, Déat had achieved the rank of captain. When the war ended in 1918, Déat finished his studies at the École Normale and went to teach philosophy in Rheims. Déat entered politics in 1926 and got elected to the Chamber of Deputies as a Socialist delegate from Marne. Déat broke away from the party in 1932 due to disagreements with Leon Blum’s policies toward Prime Minister Édouard Herriot, and as such Déat was officially expelled from the party in 1933. Without the support of the Socialists, Déat lost his seat in the Chamber of Deputies. Déat continued to stay active in Socialist politics, however, and founded the Parti Socialiste de France, whose slogan was "Order, Authority and Nation.” Two years later, Déat joined the Union Socialiste et Republicaine and returned to the Chamber of Deputies in 1936 as a delegate from Angoulême. In the same year he became Minister of Air in the government of Albert Sarraut, but he quickly resigned his post over disputes with Sarraut. He consequently lost his seat in the Chamber of Deputies.

Thoroughly disillusioned with Socialism, Déat turned to Fascism and soon became a fervent advocate of right wing politics. Déat called for France’s government to remodel itself along Fascist lines, and when it appeared as if France would go to war to Germany in 1938, Déat published the article “Why Die for Danzig?” in the newspaper L'Oeuvre. In the article, Déat argued that France should avoid war with Germany if the Nazis seized Poland. The publication caused a widespread controversy and propelled Déat to national fame. A strong supporter of Germany’s occupation of northern France in 1940, Déat took up residence in Vichy France and was initially a supporter of Philippe Pétain. When Vichy did not become the Fascist state Déat had in mind, he moved to occupied Paris and was funded by the Germans. In February of 1941, Déat founded the Rassemblement National Populaire, a collaborationist political party which espoused Anti-Semitism and totalitarianism. He also founded, along with fellow Fascist Jacques Doriot, the Legion des Volontaires Francais (LVF), a French unit of the German Army. While reviewing troops from the LVF with Pierre Laval in Versailles on August 27, 1941, Déat was wounded in an assassination attempt. After recovering, Déat became a supporter of Laval and in 1944 was made Minister of Labor and National Solidarity in Laval's cabinet (Laval became Prime Minister of Vichy France in 1942). After the Allied landings at Normandy and the fall of the Vichy government, Déat fled to Germany and became an official of the Vichy government in exile at Sigmaringen. With the fall of Germany in 1945, Déat fled to Italy and assumed a new name, temporarily teaching in Milan and Turin. He was later taken in and hidden by a religious order in a monastery near Turin, where he wrote his memoirs and lived undiscovered until his death in 1955. After the war, he had been convicted of treason and sentenced to death in absentia by a French court.